As a conventional radioactive ray detector is already known, in the following Patent Document 1, for example, a semiconductor radioactive ray detector, comprising a semiconductor element, an anode electrode attached on one surface of said semiconductor element, a cathode electrode attached on the other surface of said semiconductor element, and a signal line, one end thereof being connected with at least one of the anode electrode and the cathode electrode and the other end thereof extending straight from said electrode thereby to output a signal from that electrode.